All lenses distort in some way. As you move closer, with a wide angle lens, the part of your subject that is nearest the camera becomes larger. This happens with all lenses but short lenses will amplify the effect--this is called EXTENSION DISTORTION; and it's extremely unattractive on people! (EVIL!)
Backing away from your subject reduces this effect but then the subject becomes too small in the frame. The solution is to use a telephoto lens to increase our subject's size without distorting their features in an unattractive way.
As you back-up and use a longer lens it will push your subjects into the background--this is called COMPRESSION DISTORTION. This distortion is very useful and complimentary on people! (GOOD!)
The short lens will make the background appear to recede from your subjects and simultaneously keep the background more in focus because of the inherently greater depth of field created by the short lens. Both of these effects work against us in fine portraiture.
In portraiture we use the telephoto lens to narrow our vision, to show less (which can reveal more), to knock entire backgrounds out-of-focus and thus make our subject(s) unmistakably urgent to look at. My goal in environmental portraiture is to put my subject INTO their environment and make them look good as well. Using the telephoto lens compression effect will bind the image together not blow it apart the way a short lens does.
Where these effects are absolutely vital to control is when doing group portraiture. Even with a small group where you have them set-up in only two rows if you use a wide lens, even at a comfortable distance, you will see an increase in head sizes and body mass in the front row and a pronounced decrease in head sizes in the back row. As professionals this is something we must control!
At this point, many of you are probably asking, "So, what is he defining as a "wide-angle" that is BAD for portraits and what is a good telephoto for portraits?"
Well, many photographers reading this will probably be surprised that I define the "nifty fifty" as a wide-angle that should be avoided as much as possible--don't even think about anything wider for anything but novelty images! I don't even own a 50mm prime and have had no use for it in 40-years!
My go-to portrait lens is my Canon 70-200 f2.8 and prior to that it was my Nikkor 80-200 f2.8 when I had a Nikon system. Sometimes these were not enough when doing individuals of kids or high school seniors so I would add a 1.4X extender!
And what focal lengths am I using on who? I use the MOST telephoto I can use given the environment:
For individuals: 200-300mm usually at f2.8 to f4.5
For small families: 150mm at f5.6 to f6.3
For larger families: 135mm at f6.3 to f7.1
The portraits below show vividly the effect of EXTENSION DISTORTION (using a lens at 50mm) versus the COMPRESSION DISTORTION created using my portrait zoom at 170mm.
As always should you have questions please don't hesitate to ask!
Author: Jerry W Venz, PPA Certified Master Photographer